They are abbreviated as UPS and used widely in order to receive a continuous supply when there is no main supply available. They keep the electronic devices safe during sudden loss of power.
Types of Uninterrupted Power Supply
They are usually classified as OFF-Line UPS, ON-Line UPS and Line interactive UPS. The basic types of UPS are as follows.
OFF Line UPS
This system charges battery backup system when it is working on main power supply. When there is no supply the battery starts supplying power to the system. The figure below shows the basic block diagram representation of the OFF Line UPS system.
As the figure shows the AC supply is converted to DC rectified and stored in the battery. Incase of loss of power the transfer switch will shift down and is connected to the battery backup. This allows the continuous working of the electrical system without any interruptions.
The block diagram for the system is below. The main power supply is fed to the rectifier. The rectifier converts the AC-DC and helps the battery to charge. The output from the rectifier charges the battery and also supplies power to load after inversion.
When main power supply is present the battery is charging. The load is also getting its supply from the mains. For charging the battery we convert AC to DC and again to AC through converter. Hence we call it Double Conversion UPS. When there is no supply the battery starts to supply power to load and there is no role of rectifier in this case.
Line Interactive UPS
This is quite similar to the off line UPS except it has a tap changing transformer connected to it. The main use of transformer is for voltage regulation. The voltage regulation is done by tap changing the transformer according to the input voltage. Below shown is the representation of this system.
When there is no supply the battery supplies power through the bi-directional converter which converts the DC of the battery to AC and fed it to the transformer.
Mostly we use them in places like Hospitals, Banks, Industries, Telecommunications and data centers.
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